CD8+/TCR-graft facilitating cells (FCs) enhance engraftment of hematopoietic stem cells (HSCs) in both MHC-disparate and syngeneic recipients. FCs are a heterogeneous population of cells, with a predominant sub-population resembling plasmacytoid precursor dendritic cells (p-preDCs). FCs enhance clonogenicity of HSCs in vitro, induce antigen-specific regulatory T cells in vivo, and mediate prevention of GVHD.